Another problem in the game I am playing now. Not sure if I am just extreemly unlucky, or if there is a little bug here.
I restarted with 1.3 RC3 and are now 3 days 12 hours (roughly) in to the game. I bought my first construction vessel with 40 construction URV after 4 hours play. I have been buying 7 more CVs like that regularly since then.
I have now emptied both the HOA Shipyard in Far Out and the PMC shipyard in Ascendancy. After 84 hours of play and they have not been restocked. I have seen no ship carrying them (Believe me, I would have captured it imidietly

I went to the PMC URV parts supply near the PMC Shipyard to see if I could buy some and sell them to either the PMC or HOA shipyard. It had quite a few of pretty much any URV, just not the Construction.
I also found the LI URV BTO Line somewhere in Look Out Alpha, same thing, no Construction URV, but very high stock of pretty much anything else.
To make money I had through the game sold excess Cargolifters on my miners and freighters. I figuere that 30 Cargolifters is enough, when I capture them they usually have between 60 and 80. I make 1-2 mill on each ship. This increase the Shipyards stock of the cargolifters.
I figuere "Hey I am smart", I have a Heavy Sul with 16 construction drones, I will just have him "deliver" those to the Shipyard, I get some money for that and can buy my next Construction Vessel.
I did get the money, but the construction drones just disapeared, shipyard still at 0 stock!
So, seem like any stock of Construction Drones is simply written out of the game...
This is now to me the single biggest gamestopper and means I am not playing again :-/. Its even worse than the one I originally posted as being the worst problem for me in the game: http://forum.egosoft.com/viewtopic.php?t=365472
I could savegame edit the construction drones there, but I restarted at 1.3 with the intention of playing with NO editing at all. I have one mod running, the one that replaces the Titurels engines. This one should do nothing, as I have not even been to DeVries yet.